Actress Emma Watson has refused to be silenced by online trolls threatening to leak nude photos of her following her powerful speech on gender equality at the UN last week.

Watson's plea for men to join the fight for equal rights for women has sparked a flood of pledges across the world, including many from fellow celebrities and politicians.

"I hope we can all finally change laws and mentalities in order to establish what is nothing more than common sense," Watson posted on her Twitter account on Tuesday in response to the sinister threats.

Watson (24), who rose to fame as Hermione in the Harry Potter movies, gave her first major speech as a United Nations Women's Goodwill Ambassador in New York on Saturday, launching the "HeForShe" campaign to unite men and women for gender equality.

The initiative urges men to join the fight against violence and discrimination of women within days more than 70,000 men and boys had signed online pledges, according to the HeForShe online active map on the campaign's website.

The target is to mobilise one billion men and boys over 12 months with an online map showing exactly where men sign up. However, Watson's speech appears to have angered trolls on 4chan's b board who are now seeking retribution in the form of a smear campaign.

Setting up a countdown website that they have called EmmaYouAreNext, forum members have threatened to release nude photos of Watson. They are also attempting to get #RIPEmmaWatson trending on Twitter and are posting photoshopped pictures of news sites suggesting that Watson has died.

The very basic Photoshopped photos they have produced already suggest that any nude photos would be similar crude fakes.

Although the countdown does not specifically say that naked pictures will be published, the site is believed to have been made by members of the internet forum 4chan, who were behind the recent release of hacked pictures of celebrities such as Jennifer Lawrence and Kate Upton.

US website Gawker quoted posts, since deleted, that appear to show the timing of the release is no accident and that the publication of pictures would be a direct response to her speech. One of the comments quoted says: "She makes stupid feminist speeches at UN, and now her nudes will be online."

The hackers say they will leak nude photos of the 'Harry Potter' star in under five days' time. An image of Emma Watson wiping away a tear appears on the site beside a digital timer which is counting down the seconds until the release.

The words: "Never forget, the biggest to come thus far" are written in capital letters on the bottom of the screen.

Undress

Earlier this month Ms Watson came to the defence of her friend Jennifer Lawrence after dozens of images showing the Hunger Games actress in various states of undress were leaked on 4Chan. The actress tweeted: "Even worse than seeing women's privacy violated on social media is reading the accompanying comments that show such a lack of empathy.

More than 100 celebrities were affected by the scandal last month after an unidentified hacker stole explicit images and videos from Apple's iCloud service.

Watson, who was appointed to her U.N. role in July, received a standing ovation as she called on men and women in her speech to reclaim feminism for the benefit of all. She disclosed how she became a feminist after being told she was too "bossy" for wanting to direct a play aged eight.